A conventional inkjet printing apparatus (hereinafter referred to as a printer) has a following basic configuration.
FIG. 6 is a block diagram showing a configuration of a conventional printer. Referring to FIG. 6, numeral 1001 denotes a printer; 1002, a system controller for controlling the entire system of the printer 1001; 1003, a host interface (hereinafter referred to as a host I/F) incorporated in the system controller 1002 for communicating with an external device to exchange printing job data, printer status data and so forth; 1004, an engine controller for controlling various motors, mechanisms, an inkjet printhead (hereinafter referred to as a printhead) and so on based on data from sensors provided at various locations inside the printer 1001; 1005, an engine mainly configured with a mechanism for scanning a printhead while sequentially and intermittently conveying printing paper and for sequentially discharging ink of a designated color from the printhead to a designated position of the printing paper; and 1006, a host computer (hereinafter referred to as a host) which is a typical example of an external device that transmits printing data to the printer 1001.
In the above-described configuration, the host I/F 1003 receives a printing job sent from the host 1006, and transfers it to the system controller 1002. The system controller 1002 performs image processing on image data of the printing job, converts the image data to bitmap data that can be handled by the engine controller 1004, and transfers the bitmap data to the engine controller 1004.
Conventionally, in a case where power of such printer was managed and controlled, since the power consumed by the system controller was relatively small and since it was necessary to maintain operation of the communication function between the printer and the host, the main method of power saving was to cut off the power supplied to the main circuits of the engine and engine controller or to cut off the supply of a basic operation clock when the printer was in a sleep mode.
However, later, as demands became high for better functions and improved throughput of a printer, the circuit size of the system controller has enlarged and the speed of the CPU, memories or the like has increased, resulting in a great increase in power consumption of the system controller (e.g., refer to Japanese Patent Application Laid-Open No. 2002-103739).
For this reason, in recent years, when the printer is in a sleep mode, the power supplied to the main circuits other than the host I/F 1003 or the supply of a basic operation clock is cut off while maintaining the operation of the host I/F 1003 to perform communication with the host 1006 (see FIG. 6). In other words, when the printer 1001 is shifted from a normal operation mode (hereinafter referred to as a normal mode) to a sleep mode, the system controller 1002 and engine controller 1004 simultaneously cut off the power supplied to their main circuits or the supply of a basic operation clock. When the printer 1001 returns from the sleep mode to the normal mode, the system controller 1002 and engine controller 1004 recover the power supplied to their main circuits or the supply of the basic operation clock (e.g., Japanese Patent Application Laid-Open Nos. 2001-180083 and 2000-326590).
Meanwhile, as the image quality of the printer becomes high and the printhead adopts pigmented ink, printers requiring the following particular functions are increasing.
(1) Anti-sedimentation Process
Since pigmented ink is a solution in which pigment particles are dispersed in a solvent by a dispersion agent, sedimentation easily takes place. Therefore, if the ink is left unused for a long time, it becomes impossible to perform printing at predetermined ink density. For this reason, a printer using pigmented ink stirs ink in an ink tank at predetermined time intervals (e.g., Japanese Patent Application Laid-Open No. 2002-225304). This process is called an anti-sedimentation process.
(2) Anti-fading Process
In a printer using roll paper, roll paper processed with special surface treatment for high-quality printing is sometimes used. To convey roll paper of this type by a paper conveyance mechanism of the printer, conveyance rollers or the like apply pressure to hold the roll paper tightly, and rotation of the rollers conveys (moves) the roll paper. When printing operation is not performed (during standby), the printer stays on standby while the conveyance rollers tightly hold the roll paper. However, if the roll paper on which the aforementioned special surface treatment has been applied is left unused for a long time while being tightly held by the conveyance rollers (i.e., while pressure is applied to the paper), the pressured portion of the roll paper is faded in streaks.
Therefore, in a case where the time between one printing operation and the next printing operation is long, in order to prevent conspicuous streaked fading, the printer slightly conveys or rolls up the roll paper at predetermined time intervals so that the streaked fading is not concentrated at one location to be conspicuous (e.g., Japanese Patent Application Laid-Open No. 2002-254740). Hereinafter, such measure will be referred to as an anti-fading process.
Note that the above-described anti-sedimentation process and anti-fading process will be collectively referred to as maintenance operation.
However in the aforementioned conventional example, when the printer operation mode shifts to a sleep mode, the power supplied to the main circuits of the system controller and engine controller or the power supplied to the basic operation clock is cut off. Therefore, the aforementioned anti-sedimentation process or anti-fading process cannot be performed.
If the anti-sedimentation process and anti-fading process are not performed at predetermined time intervals, the effects of these measures are diminished.
To solve this problem, conventionally, in a case where a predetermined time period set for the anti-sedimentation process or anti-fading process has elapsed during the sleep mode, the power supplied to the main circuits of the system controller and engine controller as well as the basic operation clock is simultaneously recovered (i.e., a similar amount of power as that in the normal mode is supplied) to enable execution of the anti-sedimentation process or anti-fading process.
However, according to this countermeasure, the power supplied to the system controller and engine controller is about the same in the sleep mode and in the normal mode. Therefore, it is impossible to reduce power consumption during the sleep mode, raising an additional problem.